1. Field of the Invention
The present invention relates to a liquid droplet jetting apparatus and a piezoelectric actuator.
2. Description of the Related Art
As an ink-jet head which jets an ink from nozzles, an ink-jet head described below has hitherto been known. The ink-jet head described below has a channel unit in which, a plurality of pressure chambers which communicate with a plurality of nozzles respectively is formed, and a piezoelectric actuator which applies pressure to the ink in the plurality of pressure chambers. The piezoelectric actuator has a vibration plate which covers the plurality of pressure chambers, a piezoelectric layer which is stacked on the vibration plate, and a plurality of upper electrodes which is formed on an opposite side of the vibration plate, sandwiching the piezoelectric layer. The plurality of upper electrodes faces central portions of the plurality of pressure chambers respectively. The vibration plate is kept at a ground electric potential, and also functions as a common electrode corresponding to the plurality of upper electrodes.
When a predetermined electric voltage is applied to a certain upper electrode, an electric field parallel to a direction of thickness acts on a portion of the piezoelectric layer, facing the central portion of the pressure chambers, and the portion of the piezoelectric layer contracts in a in-plane direction. Due to the contraction of the piezoelectric layer at the central portion of the pressure chamber, an overall portion, of the piezoelectric layer and the vibration plate, facing the pressure chamber is deformed to form a projection toward the pressure chamber. Accordingly, a volume inside the pressure chamber decreases, and a pressure is applied to the ink inside the pressure chamber.